Thermal and hydrothermal treatment of UHPC: influence of the process parameters on the phase composition of ultra-high performance concrete
| Autor: | André Gardei, Sebastian Simon, Patrick Fontana, Julia von Werder, Birgit Meng |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Ettringite
Materials science Superheated steam 0211 other engineering and technologies Tobermorite chemistry.chemical_element 020101 civil engineering 02 engineering and technology Building and Construction Thermal treatment Pozzolan 0201 civil engineering chemistry.chemical_compound Compressive strength chemistry Mechanics of Materials Aluminium 021105 building & construction Pozzolanic reaction General Materials Science Composite material Civil and Structural Engineering |
| Zdroj: | Materials and Structures. 54 |
| ISSN: | 1871-6873 1359-5997 |
| DOI: | 10.1617/s11527-021-01633-w |
| Popis: | Several studies show that thermal and hydrothermal treatment can further improve the excellent properties of UHPC in terms of mechanical strength and durability. While for the thermal treatment the increase in strength is attributed to an intensified pozzolanic and hydraulic reaction, for the hydrothermal treatment previous studies accredited it mostly to the formation of tobermorite. In the presented study thermal and hydrothermal treatment of UHPC samples was systematically varied and the phase formation analysed related to the strength development of a reference sample cured for 28 days in water. For the thermal treatment the results show that the strength increase depends on the protection against desiccation and can be ascribed to an improved pozzolanic reaction of the siliceous fillers. To achieve a significant enhancement of strength, a pre-storage time of few days and a long dwell time at elevated temperature/pressure are required. For the hydrothermal treatment already heating the specimens up to 185 °C in saturated steam followed by an immediate cooling leads to a substantial increase in compressive strength. Pre-storage time did not affect the result as far as a minimum of several hours is guaranteed. The improved performance is due to an increase in the pozzolanic and hydraulic reaction. Surprisingly, tobermorite was only found within a very thin layer at the surface of the sample, but not in the bulk. Sulphate and aluminium stemming from the decomposition of the ettringite are bound in the newly formed phases hydroxylellestadite and hydrogarnet. |
| Databáze: | OpenAIRE |
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